1. Field of Disclosure
The present disclosure of invention relates to a method of driving a light source, a light source apparatus for performing the method and a display apparatus having the light source apparatus. More particularly, the present disclosure relates to a method of driving a light source while maintaining a respective luminance and a respective power consumption of the light source respectively in substantially uniform levels.
2. Description of Related Technology
Generally, it is desirable to provide a liquid crystal display apparatus with a relatively small thickness, a relatively light weight and a relatively low power consumption so that the liquid crystal display apparatus can be broadly used for mobile and other applications such as for a monitor, a laptop computer, a cellular phone, a television and so on. The typical liquid crystal display (LCD) apparatus includes a liquid crystal display panel configured for displaying an image using a light transmittance characteristic of a liquid crystal and using a light source apparatus providing a light to the liquid crystal display panel. For example, the light source apparatus may be a backlighting assembly that provides light to a back side of the LCD panel.
The light source apparatus typically includes a plurality of light sources generating a light required to display an image on the liquid crystal display panel. For example, the light sources may include at least one of a cold cathode fluorescent lamp (“CCFL”), an external electrode fluorescent lamp (“EEFL”), a flat fluorescent lamp (“FFL”), and one or more light emitting diodes (“LEDs”).
Recently, LED's having a relatively low power consumption and those being eco-friendly has been developed. The typical light source apparatus therefore includes a string of LEDs connected for example in series with each other, and a LED driver configured for driving the LED string.
A conventional light source apparatus uses a constant current driving method in which a constant current is caused to flows through the LED string to thereby energize the LED string. However, the current-voltage characteristic of LEDs often varies according to ambient temperature and/or other factors. Thus, a luminance and a power consumption of the LED may vary as local temperature varies while being driven by the constant current driving method. Accordingly, although the LED string current might be kept constant, LED string voltage and power consumption are likely to undesirably vary as a function of local temperature.
In addition to the temperature variation problem, when an LED is just turned on, the temperature of the LED is relatively low so that the luminance of the LED is relatively high. In contrast, as the duration of being turned-on increases for the LED, the local temperature of the LED tends to increase so that the luminance of the LED changes (e.g., decreases). Accordingly, a display quality of a display apparatus may decrease due to changes in ambient temperature and/or due to changes in drive duration.
It is to be understood that this background of the technology section is intended to provide useful background for understanding the here disclosed technology and as such, the technology background section may include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to corresponding invention dates of subject matter disclosed herein.